Nunberg told ABC News that he received a letter request from the committee on Friday to submit the documents by May 24. He was also asked to appear before the committee in a closed interview.

The letter, obtained by ABC News, asks for communications that mention “Russia or Russian persons, organizations, interests or WikiLeaks, Julian Assange, DCLeaks, Guccifer 2.0, or John Podesta,” from June 16, 2015, to January 20, 2017.

Julian Assange, publisher of WikiLeaks, and Guccifer 2.0, a hacker persona that U.S. intelligence services assess is tied to Russia, are accused of hacking and distributing emails taken from John Podesta, Hillary Clinton’s campaign chairman, during the 2016 campaign.

“I’m happy to appear and meet with them. I’ve never spoken to the president, I have no executive privilege issues,” Nunberg told ABC News, referring to other former Trump aides including former White House chief strategist Steve Bannon and former campaign manager Corey Lewandowski who testified before the committee but invoked executive privilege, angering its members.

The Senate Intelligence Committee is investigating Russian interference in the 2016 election.

Nunberg maintains that he has had very little written communication with Stone about the subject. Nunberg said that Stone orally told him that he had been in contact with Wikileaks founder Julian Assange and that he would publish hacked emails and information on the Clinton Foundation.

During the 2016 campaign, Nunberg also asked Stone if the information was related to the Benghazi attack but Stone said the information would mainly be related to the Clinton Foundation. Roger tweeted in August that Assange was about to release the hacked emails before the information dump.

But Nunberg told ABC News that he does not believe that Stone met with Assange, despite Stone’s prior claims.

“Roger didn’t communicate with Assange, if he had communicated with Assange then I would be concerned that he would go to jail but he didn’t,” Nunberg said.

Instead, Nunberg suggested that Stone was “lying” about his communications.

“He ingratiates himself into stories,” Nunberg said.

“I don’t think he ever did meet with Assange – why did he say that? Because it’s Roger, that’s what he does.”

In March, Nunberg testified before the grand jury in Special Counsel Robert Mueller’s investigation into Russian collusion and possible obstruction of justice.

At the time, Nunberg vowed to fight the subpoena and refused to testify, but he ended up complying.

After meeting with Mueller, he told ABC News at the time he as “very worried” about Stone coming under scrutiny from the special counsel. On the investigation, he said, “I don’t think it’s a witch hunt.”